---
title: "Scale your sending volume safely | FirstSales"
description: "Grow daily send volume without burning domains: add more mailboxes to the sender pool, let auto-adjust and warm-up ramp each one, and keep delivery protection armed."
canonical: "https://firstsales.io/tutorial/scale-sending-safely/"
---

[Home](/)/[Tutorials](/tutorial/)/Scale your sending volume safely

Deliverability

# Scale your sending volume safely

Grow daily send volume without burning domains: add more mailboxes to the sender pool, let auto-adjust and warm-up ramp each one, and keep delivery protection armed.

10 min read·Advanced·8 steps

1. 1  
## Scale with mailboxes, not with one inbox's limit  
Total campaign volume comes from how many senders it uses. Adding mailboxes to the sender pool is the safe lever; pushing one mailbox past its daily limit is not.
2. 2  
## Stand up more mailboxes  
Add mailboxes — SMTP/IMAP one-by-one, or bulk-import a CSV — on fresh or aged sending domains. Spreading across more domains isolates risk further than piling more mailboxes onto one domain.
3. 3  
## Authenticate every domain  
For each sending domain, set up **SPF**, **DKIM** (Managed DKIM for credential mailboxes), **DMARC**, and a tracking domain. Un-authenticated volume gets filtered no matter how carefully you pace it.
4. 4  
## Warm up new mailboxes first  
Don't put real campaign load on a cold mailbox. Let warm-up build reputation; **Auto-adjust** keeps the daily limit in step with **Sending health**.
5. 5  
## Set per-mailbox limits sensibly  
Leave **Auto-adjust** on and add a **Send ceiling** you're comfortable with — the range is **20–500** per day per mailbox. Keep cold mailboxes low.  
![Set per-mailbox limits sensibly](/tutorials/mailbox-limits-01-sending-config.webp)
6. 6  
## Build the campaign's sender pool  
In the campaign's **Email Accounts** selector, add the warmed, authenticated mailboxes as senders — shown as “N/M selected.” Sending now spreads across all of them.  
![Build the campaign's sender pool](/tutorials/scale-01-sender-pool.webp)
7. 7  
## Arm Delivery Protection  
Turn on auto-pause (bounce 5% / spam 0.1%) so a scaled campaign stops itself if reputation slips — essential once volume is high.  
![Arm Delivery Protection](/tutorials/autopause-02-thresholds.webp)
8. 8  
## Ramp gradually and watch health  
Add senders in waves, watch each mailbox's **Sending health** and the campaign's bounce/spam rates, and only widen the pool while the numbers stay clean.

## Pro tips

Hard-won shortcuts that keep warm-up on track.

1

### Volume = mailboxes × safe per-mailbox limit

To double sends, roughly double your warmed senders — never double one mailbox's daily limit past what's safe (500 is the hard per-mailbox ceiling).

2

### Spread across domains, not just mailboxes

Ten mailboxes on one domain share that domain's reputation. Several domains isolate blast radius if one gets flagged.

3

### Never add a cold mailbox straight to a live campaign

Warm it first; auto-adjust and warm-up exist precisely so you don't hand-tune a ramp.

4

### Scaling without auto-pause is gambling

The one setting that saves you at volume is Delivery Protection — arm it on every campaign before you widen the sender pool.

## Frequently asked questions

How do I send more emails per day?

Add more warmed, authenticated mailboxes to the campaign's sender pool. Volume scales with senders, not by raising one mailbox's limit.

Is there a mailbox rotation setting?

No — “rotation” just means selecting multiple sender mailboxes; FirstSales spreads sends across whichever ones you assign.

What's the per-mailbox limit?

**20–500** emails/day, default 50, with **Auto-adjust** ramping it from Sending health. Scale by adding mailboxes, not by exceeding 500 on one.

Do I need to warm up every new mailbox?

Yes — a cold mailbox on real volume tanks deliverability. Warm it up first; auto-adjust respects warm-up health.

Does each domain need its own authentication?

Yes — **SPF/DKIM/DMARC** and a tracking domain per sending domain, or the extra volume just gets filtered.

How do I protect a high-volume campaign?

Arm **Delivery Protection** (auto-pause on bounce 5% / spam 0.1%) so it stops itself before reputation damage spreads.

Should I use one domain or several?

Several — spreading mailboxes across domains isolates the blast radius if one domain gets flagged.

How fast can I ramp?

In waves. Add senders gradually, watch each mailbox's Sending health and the campaign's bounce/spam rates, and widen only while metrics stay clean.

## Ready to put this into practice?

Start your FirstSales trial and launch a warmed, authenticated mailbox in minutes.

[Start for $1](https://app.firstsales.io)

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